1. Field of the Invention
The present invention relates to torque wrenches of the type which produce an indication of the torque level applied by the wrench to an associated workpiece. In particular, the present invention relates to electronic torque wrenches of the type which produce an output signal when the torque applied equals or exceeds a predetermined torque level.
2. Description of the Prior Art
Electronic torque wrenches typically include an elongated deflection beam provided at one end with a head portion for coupling to an associated workpiece, such as a threaded fastener or the like, and provided at the other end with an elongated handle. Strain gauges are mounted on the deflection beam to measure the strain or deflection of the beam in response to forces applied to the handle by the operator in applying torque to an associated workpiece. Typically, the strain gauges are connected in an electronic circuit which produces an indication of the torque applied to the workpiece as a function of the measurements made by the strain gauges. Output signals may be produced, either directly indicating the amount of torque applied, or indicating when the torque applied equals or exceeds a predetermined torque level.
In prior art torque wrenches, various types of indications have been utilized. Meters or gauges may give direct visual indications of the torque level applied, or may give a visual indication, such as by an illumination of a lamp or the like when a predetermined torque level is exceeded. It is also known to provide audible alarm signals to indicate that the predetermined torque level has been exceeded.
Torque wrenches are commonly used by mechanics, such as auto mechanics, who are frequently working in confined spaces, such as beneath a motor vehicle. In such circumstances, either because of the space limitations of the work area or the available light level, or both, he may be unable to see a visual indication on the wrench. For example, such mechanics frequently use torque wrenches in situations where the visual indicator on the wrench is facing away from the user in use, so that it cannot be seen by him. Also, auto repair shops and the like, where torque wrenches are commonly used, are typically noisy environments, with vehicle engines running, power tools being operated and the like, so as to create a level of background noise which makes it difficult or impossible for the operator to clearly hear an audible indication from the torque wrench.